Modifications are alterations to weapons and armor that improve their characteristics and add new features. They are performed by technicians in exchange for money. Some modifications requires special tools that you must acquire for the technician before he can apply the modification.

Each weapon and armor usually has one or more chains of modifications with up to three individual links. For most chains, to get the last modification you must first buy a modification in each of the previous links. Some links have an option of two modifications in which case you can buy one, but not both, of them; this means that you usually cannot buy every single modification for a weapon or armor since some modifications rule others out. This is demonstrated in the following example:

Each column is a link in a chain. The example above has two chains. To buy Modification 4, you must first buy Modification 1, followed by a choice between either Modification 2orModification 3. Modification 5 and 6 are in a separate chain, and your choices of Modifications 1-4 does not affect them.

Some chains do not require modifications in previous links to be bought; these chains usually deal with various improvements such as caliber change and scopes for weapons, and nightvision for body armors.

Also note that if you modify a weapon, all attachments will be taken off the weapon, and it will also be unloaded of any ammunition - this is important to keep in mind since you'll need to reload your weapon before you can use it; you dont want to walk into a firefight with a fully modified weapon only to realize that it's empty.

As mentioned earlier, some modifications require that the technician has the right tools for the job. In each modification (see the examples above) the requirements are noted in two places; the first is the title of the modification, which has a background color indicating the requirement, and the second is at the bottom which has a textual description. The title colors are as follows:

Technicians can also reapir weapons and armor, which is quite useful for several reasons; you can save money by repairing your current equipment rather than having to buy new weapons and armor. Also, you can acquire unique items that cannot be easily replaced (or which may be very expensive), so having the option to repair is a sure way to extend their lifespan. On the Weapons and Armor pages you can see how much the different items cost to repair (without discounts) if they are in the worst possible condition, which can be used as a basis for determining how costly your gear is to keep in good condition. The price of repairs depends on the current condition of any weapons and armor you have; the worse the condition is, the more it's going to cost you to have repaired.

Please note that the prices listed for modifications and repairs are the default prices without any discounts. You may get two discounts at Cardan - 10% and 20%, respectively - if you bring him one or two bottles of vodka; these discounts are substantial and you can easily save hundreds of Rubles by making sure he's boozed up before buying any repairs or modifications. Also, Cardan does require vodka before he can perform most modifications. Once you've brought him the broken Gauss Rifle he will stay sober for the rest of the game, and no longer require any alcohol; his 20% discount will become permanent at this point. Nitro will give a permanent 20% discount if you get him some radio materials - refer to this page for information about the optional mission.